Fix help message for Cluster's --features argument

The Cluster app's help message for the --features argument was
previously printing out the possible values for distance functions
rather than the possible values for features.
Merge pull request #10 from njwilson/fix-features-help

Fix help message for Cluster's --features argument
Added files for checking HW2.
Increase version to 0.3.0
Add stub files for HW4.
Update README, prepare for 0.3.0 release.
Add --output-dispersion (-d) option
Implement support for the --show-dispersion option
Merge pull request #11 from njwilson/output-dispersion

Add option for outputting dispersion
Merge remote-tracking branch 'upstream/master'

Conflicts:
	src/main/scala/appliednlp/app/Cluster.scala
Problem 3
Problem 4
Problem 5
Merge branch 'homework4' -- hacky hacky hacky